$(function(){
  //get elem: range（滑杆）,span(年龄输出)
  
  let $range = $('input'),
      $age   = $('span');

  //range change event
  $range.change(()=>{
    //get range value
    //set span text
    
    $age.html($range.val()); //<span></span>
  })
});

